The present invention relates to plumbing fixtures and components, and more particularly, to flush valves for toilet tanks.
A conventional gravity operated flush toilet has several basic components. The china components include a bowl and a water tank mounted on top of a rear portion of the bowl. The bowl and water tank are usually separate pieces joined together, and such an arrangement is hereafter referred to as a two-piece toilet. The plumbing components of a conventional gravity operated flush toilet include a fill valve in the tank that is connected to a water supply line, a flush valve mounted in a hole in the bottom wall of the tank that communicates with the bowl, a flapper valve that normally closes the flush valve, and a lever or push button on the outer wall of the tank that is connected with a chain or other mechanical linkage for momentarily lifting the flapper valve. This allows water stored in the tank to flow rapidly through the flush valve into the bowl to carry waste along with the water through a trap connected to the underside of the bowl and into a waste pipe connected to a sewer line, septic tank or other waste reservoir.
Conventional flush valves for two-piece gravity operated toilets are generally cylindrical and provide a round valve seat for the flapper valve. They are secured in a drain hole in the bottom wall of the toilet tank from underneath the bottom wall. Typically a large nut is screwed over a male threaded lower portion of the cylindrical flush valve body, on the underside of the bottom wall of the tank. See for example U.S. Pat. No. 4,155,128 of Dyer entitled TOILET TANK FLUSH VALVE ASSEMBLY. This is readily accomplished before the tank is mated with the bowl.
Modern gravity operated toilets frequently are made with a one-piece china component in which the bowl and the tank are formed as a one continuous integral piece of porcelain. In such one-piece toilets manual access to the underside of the bottom wall of the tank is severely restricted. This is because a channel from the tank to the toilet bowl and/or a toilet siphon leg is cast directly underneath the toilet tank. Thus the drain hole is a so-called "blind hole". Because there is no ready way to access the underside of the bottom wall of the tank it is very difficult, if not impossible, to thread a large nut over an externally threaded bottom portion of a cylindrical flush valve body.
Various solutions have been proposed for top mounting a flush valve in a blind drain hole in the bottom wall of a toilet tank. A series of screw fasteners can extend through the flush valve body or its throat to engage a spanner or a series of tabs that can be drawn up against the underside of the bottom wall of the tank. This is tedious and such hardware can restrict or diminish flow. Alternatively, U. S. Pat. No. 4,433,466 of Grimstad discloses an arrangement in which the drain hole has a triangular configuration. The flush valve body has three equally spaced radially extending tab-like projections that can be inserted through the irregular shaped drain hole. Once inserted, the flush valve body can be rotated so that the projections engage the underside of the bottom wall of the toilet tank. A resilient seal surrounding the valve body is squeezed between the upperside of the bottom wall of the toilet tank and a flange or shoulder on the flush valve body when the projections are engaged against the underside of the bottom wall of the tank. One drawback of this approach is that the flush valve is not truly locked in position and can be dislodged if inadvertently twisted. Furthermore, homeowners and other non-plumbers my not correctly orient the flush valve after replacing the seal, and leaks can result. In addition, it is not possible to produce a universal top mounted flush valve where one design must be configured for irregular blind drain holes and another design configured for round drain holes.
U.S. Pat. No. 5,692,249 of Johnson discloses another top mounted flush valve for a toilet tank. It includes a draw collar which can be rotated to outwardly collapse a seal barrel portion of a deformable seal member against the underside of the bottom wall of the toilet tank. While this invention has been commercialized with some success, it has several drawbacks. The seal member may harden over time due to the effects of chlorine in the water. This may make it extremely difficult to remove the seal member to allow replacement of the same. Also, the co-molded seal and nut in the commercial version of this invention can break down over time and leakage can result.